What does it mean to set the shutter speed to the reciprocal of the sensitivity in photography?

This may be a summary of some kind of experience. ...

But in fact, this calculation method is meaningless. ...

Because:

1, the iso should be as low as possible when shooting, so as to ensure pure image quality. Gao gan can't open it.

2. Shutter speed is not only determined by iso, but also closely related to aperture, focal length and photometry. But also related to these parameters. The so-called safety shutter refers to the reciprocal of the focal length.

3. The shooting parameters need to be set flexibly according to the shooting environment and shooting requirements, and there is no certain rule. You can't carve a boat for a sword.